1. Field of the Invention
The invention relates to an optical recording system, more particularly to an optical recording system capable of switching from a constant angular velocity recording mode to a constant linear velocity recording mode.
2. Description of the Related Art
A conventional optical recording device can be operated in two recording modes, i.e., constant angular velocity (CAV) recording mode and constant linear velocity (CLV) recording mode. In the CLV recording mode, the rotation speed of the spindle motor is decreased in proportion to a radius of a disc as a recording point goes outward such that data recording needs much time. In the CAV recording mode, the recording speed is increased in proportion to a radius of a disc as a recording point goes outward. However, if the recording speed is faster than a threshold recording speed, data recorded on the disc cannot be read as a result of erroneous or incomplete recording of data.
Therefore, in order to solve the above problems, U.S. Patent Publication No. US-2002-0003761 discloses a method of changing a recording mode, in which a recording speed is detected from a wobble signal reproduced while recording data to a writable disc in the CAV recording mode, and a change from the CAV recording mode to the CLV recording mode is conducted if the detected recording speed exceeds a predetermined threshold.
However, when a spindle motor for driving rotation of the writable disc rotates unstably such that a poor wobble signal may be reproduced, the exact recording speed cannot be detected, and precise changing from the CAV recording mode to the CLV recording mode cannot be ensured.